To continue to investigate the effects of hypertension on the large arteries of the rat using various tracers and surface stains for electron microscopy. To study in the rat the effects of reduction in blood pressure to normal on the intimal lesions previously produced by hypertension. To study the effect of various types of hyperlipemia on the arterial intima. To continue an investigation in the rat into the thrombotic effects of combined hypertension and raised levels of free fatty acids. To correlate transmission and scanning electron microscopic appearances in the investigations 1, 3 and 4 above.